1. Field of the Invention
The present invention relates to a display control system with a control of background luminance and color. The system according to the present invention is used, for example, for a display control in a personal computer.
2. Description of the Related Arts
In a prior art display control system, for example, of the paper-white display type, a character pattern video signal, a character video red signal, a character video green signal, a character video blue signal, a character video intensity signal, a graphic video red signal, a graphic video green signal, a graphic video blue signal, and a graphic video intensity signal are used.
The priority between a character video selection signal and a graphic video selection signal is determined by a video signal priority circuit.
The synthesis of the video signal is carried out in a video signal synthesis portion on the basis of the character video selection signal and the graphic video selection signal with the determined priority and a video enable signal generated in a video enable signal generation circuit. The output of the video signal synthesis portion is supplied to a cathode ray tube as a display device.
In order to form a background having a selectable luminance tone or a selectable color on a display plane of the display device in the prior art system, it is necessary to form such a background either by inverting the signal for the character or by constituting the background from the graphic video red, green, blue, and intensity signals.
However, in the prior art system, a problem arises in that the adjustment of the background luminance tone or the background color is difficult to adequately attain. Also, there is a problem in that the viewing of a character becomes difficult when the position of the character is on the border between the picture range and the edge range, since an edge of the character which is displayed in black color continues into the same black color of the edge range on the display plane, so that discrimination of the character from the edge range on the display plane becomes difficult.